This invention relates to systems and methods of controlling a vehicle, especially a heavy vehicle such as a highway truck or a tractor, in particular by controlling the vehicle's fifth wheel.
Over-the-highway trucks and tractor-trailer combinations come in many different sizes and configurations, and the relative geometry of the tractor and trailer in a load-carrying vehicle such as a class-8 tractor-trailer combination can vary widely. For example, the distribution of a tractor-trailer's weight on its axles can vary based on, among other factors, the position of a “fifth wheel” with respect to the cab of the tractor. A “fifth wheel” is generally a wheel or portion of a wheel placed horizontally over the rear axle or axles of a tractor or truck that is a coupling for a trailer.
FIG. 1 is a side view of a typical tractor 100 having a cab 102, front wheels and axle 104, a pair of rear wheels and axles 106, and a fifth wheel 108. Some tractors have sliding fifth wheels, which can be used to manage vehicle weight distribution by moving the trailer closer to or farther from the tractor. For example, U.S. Pat. No. 4,429,892 to Frampton et al. describes a device for attachment to a tractor for selectively moving the fifth wheel assembly of the tractor. The device has two drive members that can be extended or contracted from the cab of the tractor to slide the fifth wheel back and forth.
For safety, the fifth wheel should not be permitted to slide when the vehicle is moving. U.S. Pat. No. 6,384,716 to Eckelberry describes a trailer slider positioning alarm. The slider (fifth wheel) is locked in place with a set of pins. A speed sensor detects a speed of the unit and a pin position sensor detects whether any of the pins are unlocked. An alarm sends an alert signal in response to the speed sensor's detection of a predetermined speed and the pin position sensor's detection of at least one unlocked pin.
Some sliding fifth wheels, like other truck components, are actuated by pneumatic pressure that is controlled from the dash in the cab of the tractor. Actuating a switch on the dash locks and unlocks the position of the fifth wheel. The fifth wheel slide lock may be activated by an electrically controlled air solenoid or similar device.
The pneumatic supply to a bank of air solenoids, including the fifth wheel slide solenoid, usually uses a common feed. Because the air supply is shared by other truck components, a pneumatic interlock cannot be provided for the fifth wheel slide and so the fifth wheel slide can be released at any vehicle speed simply by activating the slide switch on the dash of the truck. If the fifth wheel slide is released while the vehicle is moving, the truck or trailer fifth wheel components could be damaged.